Information about the codes that appear on passenger vehicle tires as well as other useful information can be found in the National Highway Traffic Safety Administration (NHTSA) brochure, "Tire Safety, Everything Rides On It.": http://www.nhtsa.dot.gov/cars/rules/TireSafety/ridesonit/brochure.html
For additional information, please contact the NHTSA Office of Vehicle Safety Compliance by calling
(202) 366-5291.
If the FAQ above did not lead you to the answer to your question:
You can browse by category at the top of the page.